The Great Demon King, or Beelzebub III, is a very random and forgetful king. He wants to Destroy humanity and sends his youngest son Beelzebub IV to the human world to do the job for him. He decides later to send his older son instead, but forgets that he already sent his youngest son to do that. After he is reminded by his servants, he sends his first son En to do the job with his little brother.